What Is Water Limitation?

Due to the severity of water limitation on crop productivity, experiments identifying mechanisms involved in resistance to water limitation are becoming more prevalent. Yet the term water limitation has taken on many meanings and, as a result, implementation of water limitation regimes can be inconsistent and comparison of results across experiments is difficult. As such, we are interested in investigating the commonalities and differences of three water limitation stresses, focusing our efforts on variation in gene expression. Changes in gene expression were monitored in the oilseed crop, Helianthus annuus, following exposure of seedlings to high salinity (100 mM NaCl), osmotic stress (8.25% polyethylene glycol), or a repeated soil dry down, where plants were rewatered every other day. Upon analysis, 26 217 unique genes were used to examine gene expression in roots and leaves at 10 days post-treatment. Of this original gene set, 1 906 unique genes, 1 264 in the roots and 642 in the leaves, were differentially expressed across the three water limitation stresses in relation to a well watered control, sampled at the same time. Of these unique genes, there were fewer shared across all stresses than within individual stressors. Further, the polyethylene glycol and salinity stresses shared more differentially expressed genes than any other pairwise stress combination in both tissues, indicative of a similar stress response. Overall, this study provides an informational foundation on cultivated sunflower’s water limitation response, which will accelerate follow up QTL, transcriptomic, and comparative studies.